System and method for controlling haptic devices having multiple operational modes

ABSTRACT

A haptic device having a plurality of operational modes, including a first operational mode and a second operational mode is provided. The first operational mode is associated with a frequency range. The second operational mode is associated with a frequency range that is different from the frequency range of the first operational mode. A controller is coupled to the haptic device, and is configured to send the haptic device a plurality of control schemes. Each control scheme is uniquely associated with an operational mode from the plurality of operational modes. 
     Another embodiment provides a method that includes providing power to a haptic device configured to cause the haptic device to provide a haptic sensation above a pre-determined sensation threshold. A voltage pulse that is configured to change the haptic sensation output by the haptic device by a pre-determined amount within a pre-determined time period is also applied to the haptic device.

PRIORITY

This is a continuation application of U.S. patent application Ser. No.12/818,618 filed on Jun. 18, 2010, which is a divisional application ofU.S. patent application Ser. No. 10/873,643, filed on Jun. 23, 2004,issued as U.S. Pat. No. 7,742,036 on Jun. 22, 2010, which claimspriority of U.S. Provisional Application No. 60/530,979 filed Dec. 22,2003. The disclosure of each of the above-listed applications is hereinincorporated by reference.

BACKGROUND

The invention relates generally to haptic feedback devices. Morespecifically, the invention relates to controlling haptic devices eachhaving multiple operational modes.

Computer users often use interface devices to provide information tocomputers or other electronic devices. For example, with such interfacedevices, a user can interact with an environment displayed by a computerto perform functions and tasks on the computer, such as playing a game,experiencing a simulation or virtual reality environment, using acomputer aided design system, operating a graphical user interface(GUI), or otherwise affecting processes or images depicted on an outputdevice of the computer. Common human interface devices for computers orelectronic devices include, for example, a joystick, button, mouse,trackball, knob, steering wheel, stylus, tablet, pressure-sensitiveball, remote control, wireless phone, and stereo controls.

In some interface devices, feedback, such as force feedback, can also beprovided to a user. Each of these interface devices, for example,includes one or more haptic devices, which are connected to acontrolling processor and/or computer. Consequently, by a controllingprocessor, controller, and/or computer, haptic forces produced by thehaptic device can be controlled in coordination with actions of the userand/or events associated with an audible environment or a graphical ordisplayed environment by sending control signals or commands to hapticfeedback device.

Multi-mode haptic devices that provide desirable performance have beendeveloped. For example, U.S. application Ser. No. 10/301,809, entitled,“Haptic Feedback Using Rotary Harmonic Moving Mass,” the entiredisclosure of which is incorporated herein by reference, discloseshaptic feedback using a device having a rotary harmonic moving mass.Accordingly, additional systems and methods for controlling multi-modehaptic devices are desirable.

SUMMARY

An embodiment of the invention provides a system and method forcontrolling multi-mode haptic devices. A haptic device having multipleoperational modes, including a first operational mode and a secondoperational mode is provided. The first operational mode is associatedwith a frequency range. The second operational mode is associated with afrequency range that is different from the frequency range of the firstoperational mode. A controller is coupled to the haptic device, and isconfigured to send the haptic device multiple control schemes. Eachcontrol scheme is uniquely associated with an operational mode from themultiple operational modes. According to an embodiment of the invention,the controller is configured to combine each control scheme from themultiple control schemes prior to sending the multiple control schemesto the haptic device.

Another embodiment of the invention provides a method that uses avoltage pulse to reduce the response time of a device. According to thismethod, steady-state power is provided to a haptic device that isconfigured to cause the haptic device to output a haptic sensation abovea pre-determined sensation threshold. A voltage pulse, which isconfigured to change the haptic sensation output by the haptic device bya pre-determined amount within a pre-determined, reduced response time,is applied to the haptic device. According to an embodiment of theinvention, the voltage pulse is applied to the haptic device prior toproviding the steady-state power to the haptic device. According toanother embodiment, the voltage pulse is applied to the haptic deviceafter terminating the steady-state power provided to the haptic device.The voltage pulse can be applied to a single-mode haptic device or amulti-mode haptic device. According to one or more embodiments of theinvention, use of such a voltage pulse can improve response time of ahaptic device to which the pulse is applied (e.g., for stopping orstarting haptic effects, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system including a processor system andan interface device, according to an embodiment of the invention.

FIG. 2A is a diagram illustrating a haptic device, a controller, and asensor, according to an embodiment of the invention.

FIG. 2B is a block diagram of a haptic device, according to anembodiment of the invention.

FIG. 3A is a perspective view of a haptic device, according to anembodiment of the invention.

FIG. 3B is a cross-sectional view of the haptic device shown in FIG. 3A.

FIG. 4A is a perspective view of a haptic device, according to anembodiment of the invention.

FIG. 4B is a cross-sectional view of the haptic device shown in FIG. 4A.

FIG. 5 shows a top view of a portion of a haptic device, according to anembodiment of the invention.

FIG. 6 shows a top view of a portion of a haptic device, according to anembodiment of the invention.

FIG. 7 shows a top view of a portion of a haptic device, according to anembodiment of the invention.

FIG. 8 is a plot showing an acceleration-versus-time response of ahaptic device, according to an embodiment of the invention.

FIG. 9 is a plot showing an acceleration-versus-time response of ahaptic device, according to an embodiment of the invention.

FIG. 10 is a plot showing drive-signal frequency ranges of a multi-modehaptic device, according to an embodiment of the invention.

FIGS. 11A-11G are plots showing examples of signals used to drive ahaptic device, according to an embodiment of the invention.

FIGS. 12A-12C are plots showing examples of signals used to drive ahaptic device, according to an embodiment of the invention.

FIGS. 13A-13E are plots showing examples of signals used to drive ahaptic device, according to an embodiment of the invention.

FIG. 14 is a plot showing an example of a signal used to drive a hapticdevice, according to an embodiment of the invention.

FIG. 15 is a diagram illustrating elements of an embodiment of theinvention.

FIG. 16 is a plot showing an example of a signal used to drive a hapticdevice, according to an embodiment of the invention.

FIG. 17 is a plot showing an example of a signal used to drive a hapticdevice, according to an embodiment of the invention.

FIGS. 18A-18C are plots showing examples of signals used to drive ahaptic device, according to an embodiment of the invention.

FIG. 19A is a plot showing an example of a step signal used to drive ahaptic device and the corresponding response of the haptic device,according to an embodiment of the invention.

FIG. 19B is a plot showing an example of a signal used to drive a hapticdevice and the corresponding response of the haptic device, according toan embodiment of the invention.

FIG. 20A is a plot showing an example of a step signal used to drive ahaptic device and the corresponding response of the haptic device,according to an embodiment of the invention

FIG. 20B is a plot showing an example of a signal used to drive a hapticdevice and the corresponding response of the haptic device, according toan embodiment of the invention.

DETAILED DESCRIPTION

Systems and methods for controlling multi-mode haptic devices aredescribed. More specifically, an embodiment of the invention isdescribed in the context of a haptic device that has a multipleoperational modes, each of which is associated with a frequency range. Acontroller is coupled to the haptic device and is configured to send thehaptic device multiple control schemes associated with the multipleoperational modes.

Feedback provided via a haptic device is sometimes referred to asvibrotactile feedback or kinesthetic feedback, and is referred to moregenerally herein as “haptic feedback.” Such haptic feedback can beprovided, for example, by way of a haptic device or an interface deviceincluding a haptic device. Interface devices that provide hapticfeedback can provide physical sensations that can be measured by somemetric (e.g., perceivable frequency content), and can be felt by a userusing a controller or manipulating a physical object of the interfacedevice.

According to an embodiment of the invention, a haptic device hasmultiple operational modes. A first operational mode is associated, forexample, with a high-frequency range, and a second operational mode isassociated, for example, with a low-frequency range control schemeassociated with each of the operational modes can be sent to the hapticdevice; each of the control schemes can cause the haptic device toprovide a particular haptic feedback. The control scheme associated witheach frequency range can be combined (e.g., superimposed, added,multiplied, convolved, combined by a non-vectored operation, etc.) withone or more remaining control schemes, or otherwise operated on,according to pre-determined rules to provide a transitional responsebetween the frequency ranges. In this manner, an embodiment of theinvention provides for a “blending” or “transitioning” of hapticfeedback from a low-frequency range to a high-frequency range such thatthe performance over and between the low- and high-frequency ranges isrelatively seamless.

According to another embodiment of the invention, a haptic device havingmultiple operational modes is provided. The multiple operational modesof the haptic device include, for example, a low-frequency operationalmode, a high-frequency operational mode, and a transitional operationalmode, which is associated with frequencies between low frequenciesassociated with the low-frequency mode and high frequencies associatedwith the high-frequency mode. The low-frequency operational mode issometimes referred to herein as “unidirectional” (e.g., unidirectionalspinning of a rotational device), and the high-frequency operationalmode is sometimes referred to herein as “harmonic” or “oscillating.” Thetransitional operational mode is associated with a transitionalfrequency range that combines a superposed response of theunidirectional mode and the harmonic mode. The low-frequency operationalmode is associated with, for example, frequencies up to approximately 10Hz, and the high-frequency operational mode is associated withfrequencies, for example, above approximately 10 Hz. A transitionalfrequency range associated with the transitional operational modeincludes, for example, frequencies from about 5 Hz to about 25 Hz, wherethe low-frequency and high-frequency operational modes are associatedwith frequencies below and above the transitional frequency range,respectively.

FIG. 1 is a block diagram of a system having a processor system 10 andan interface device, according to an embodiment of the invention. Thesystem illustrated in FIG. 1 includes a processor system 10 incommunication with an interface device 20. The processor system 10 canbe, for example, a commercially available personal computer or a lesscomplex computing or processing device that is dedicated to performingone or more specific tasks. For example, the processor system 10 can bea terminal dedicated to providing an interactive virtual realityenvironment, such as a gaming system, or the like.

The processor system 10 includes a processor 12, which according to oneor more embodiments of the invention, can be a commercially availablemicroprocessor. Alternatively, the processor 12 can be anapplication-specific integrated circuit (ASIC) or a combination ofASICs, which is designed to achieve one or more specific functions, orenable one or more specific devices or applications. In yet anotheralternative, the processor 112 can be an analog or digital circuit, or acombination of multiple circuits.

Alternatively, the processor 12 can optionally include one or moreindividual sub-processors or coprocessors. For example, the processorcan include a graphics coprocessor that is capable of renderinggraphics, a controller that is capable of controlling one or moredevices, a sensor that is capable of receiving sensory input from one ormore sensing devices, and so forth.

The processor system 10 also includes a memory component 14. As shown inFIG. 1, the memory component 14 can include one or more types of memory.For example, the memory component 14 can include a read only memory(ROM) component 14A and a random access memory (RAM) component 14B. Thememory component 14 can also include other types of memory notillustrated in FIG. 1 that are suitable for storing data in a formretrievable by the processor 12. For example, electronicallyprogrammable read only memory (EPROM), erasable electricallyprogrammable read only memory (EEPROM), flash memory, as well as othersuitable forms of memory can be included within the memory component 14.The processor system 10 can also include a variety of other components,depending upon the desired functionality of the processor system 10.

The processor 12 is in communication with the memory component 14, andcan store data in the memory component 14 or retrieve data previouslystored in the memory component 14. The components of the processorsystem 10 can communicate with devices external to the processor system10 by way of an input/output (I/O) component 16. According one or moreembodiments of the invention, the I/O component 16 can include a varietyof suitable communication interfaces. For example, the I/O component 16can include, for example, wired connections, such as standard serialports, parallel ports, universal serial bus (USB) ports, S-video ports,large area network (LAN) ports, small computer system interface (SCSI)ports, audio ports, and so forth. Additionally, the I/O component 16 caninclude, for example, wireless connections, such as infrared ports,optical ports, Bluetooth wireless ports, wireless LAN ports, or thelike.

By way of the I/O component 16, the processor system 10 can communicatewith other devices, such as interface devices 20. These interfacedevices 20 can be configured to provide haptic feedback. Each interfacedevice 20 can communicate with the processor system 10 by way of an I/Ocomponent 16 a, which is similar to the I/O component 16 of theprocessor system 10 and can include any of the wired or wirelesscommunications ports described above in connection with that I/Ocomponent 16. Thus, the communications link between the I/O component 16of the processor system 10 and the I/O component 16 a of the interfacedevice 20 can take a variety of forms, including, for example, wiredcommunications links, wireless communications links (e.g., RF links),optical communications links, or other suitable links.

The interface device 20 includes a number of components, such as aprocessor 22, a haptic device 24, and a sensor 26. As with thecomponents of the processor system 10, the interface device 20 caninclude additional components. For example, the interface device caninclude additional duplicates of the components shown in FIG. 1 (e.g.,the interface device 20 can include multiple processors 22, hapticdevices 24, sensors 26 and/or controllers 30, etc.). Additionally, theinterface device 20 can include other components not shown in thefigure. For example, where it is desirable to store data received by theinterface device 20 via I/O component 16 a, a suitable memory componentor buffer memory component can be used. The interface can also includepower-sourcing circuitry, an example of which can be seen in U.S. Pat.No. 5,929,607, entitled, “Low Cost Force Feedback Interface withEfficient Power Sourcing,” the disclosure of which is incorporated byreference herein in its entirety.

The processor 22 of the interface device 20, can be similar to theprocessor 12 of the processor system 10, described above, or can bespecifically designed (e.g., an ASIC) and/or programmed for thefunctionality of the interface device 20. As with the processor 12 ofthe processor system 10, the processor 22 of the interface device 20,can include a variety of sub-processors, which can, for example, be usedin parallel.

As discussed above, the interface device 20 includes a haptic device 24,which is used to provide tactile or haptic feedback to a user of theinterface device 20. According to an embodiment of the invention, hapticfeedback can be provided by way of a physical object, such as a housing,a manipulandum, or the like. The haptic device 24 can take a variety offorms, including one or more haptic devices that each have multipleoperational modes associated with multiple corresponding frequencyranges. Some examples of haptic device 24 configurations that can beused in accordance with one or more embodiments of the invention will bedescribed in greater detail below. The examples of haptic devices 24given below, however, are not intended to form an exhaustive list of alltypes of haptic devices 24 that can be included in the interface device20 but are intended instead as examples only.

The sensor 26 of the interface device 20 is configured to sense inputfrom a user of the interface device 20. For example, the sensor 26 canbe used to sense manipulation or movement of a physical object, such asa manipulandum, of the interface device 20. The sensor 26 can also beused to sense other forms of user input, such as pressure, speed,acceleration, torque, light, or other measurable quantities. Forexample, the sensor 26 can incorporate a piezoelectric sensor to sensepressure, an inertial measurement unit (IMU), such as an accelerometer,to sense various forms of motion, a photovoltaic sensor to sense changesin light levels, and/or other sensors. The sensor 26 can also senseother input, such as feedback (e.g., state information includingposition and/or velocity) from the haptic device 24, for example.

As shown in FIG. 1, the various components of the interface device 20are in communication with one another and with the components of theprocessor system 10 (via the I/O components 16, 16A). The processor 22of the interface device 20, for example, can be used to control thehaptic device 24 based on information received from the sensor 26.Similarly, the processor 12 of the processor system 10 can be used tocontrol the haptic device 24 of the interface device 20 based oninformation received from the sensor 26 of the interface device 20; insuch an embodiment, the processor 22 need not be present. Alternatively,the processor 12 of the processor system 10 (also referred to as a “hostprocessor”) can be used in concert with the processor 22 of theinterface device 20 (also referred to as a “local processor”) both tointerpret data received from the sensor 26 and to control the hapticdevice 24.

The processor system 10 and the interface device 20 can optionally makeuse of one or more controllers 30 a, 30 b, 30 c, 30 d (which can bereferred to hereinafter as a controller 30, collectively, individually,or as a subset). As shown in FIG. 1, a controller 30 can exist withinthe processor 12 (e.g., in the form of a control algorithm) of theprocessor system 10 and/or the processor 22 of the interface device 20.Additionally, a controller 30 can be a separate component connected tothe other components of the processor system 10 and/or the interfacedevice 20 via a bus or other suitable connection. It should berecognized that, according to one or more embodiments, the interfacedevice 20 can function independently of the processor system 10, as ithas its own processor and/or controller 30 c, 30 d, and may not requirea processor system 10 at all. For example, the interface device 20 canbe a stand-alone device such as a personal digital assistant (PDA) or acellular telephone, which may or may not be configured to connect to aprocessor system 10.

FIG. 2A is a diagram illustrating a haptic device, a controller, and asensor, according to an embodiment of the invention. FIG. 2A also showsdifferent data values provided to the system. The elements shown in FIG.2A can be used with the processor system 10 and the interface device 20,or with the interface device 20 alone.

As shown in FIG. 2A, user input 28 can optionally be provided (e.g., viathe user interface device 20 shown in FIG. 1), and received by anoptional sensor 26. The user input 28 can also optionally be provideddirectly to a controller 30 (e.g., by way of the sensor 26, or someother devices configured to accept and convey user input). The sensor 26can also optionally receive information from the haptic device 24. Forexample, the sensor 26 can sense the actual movements of the hapticdevice 24, thereby sensing the tactile or haptic feedback output by thehaptic device 24.

According to an arrangement of the system shown in FIG. 2A, thecontroller 30 can optionally receive data from the sensor 26, and canoptionally receive user input 28 and control parameters 32. Based on theany data received from the sensor 26, any received user input 28, and/orany received control parameters 32, the controller 30 controls thetactile output or haptic feedback of the haptic device 24. For example,the controller 30 (or control algorithm when so implemented) can be usedto implement a feedback algorithm, controlling the haptic device 24based on feedback received from the haptic device 24. The controllercontrols the output of the haptic device 24 by a control signal that thecontroller 30 outputs to the haptic device 24.

The control signal output by the controller 30 can be based on a numberof parameters, including, for example, control parameters 32. Forexample, control parameters 32 and other parameters that are used by thecontroller 30 to control the haptic device 24 can be stored in thememory component 14 of the processor system 10, or by another suitablememory component (e.g., a memory component of the interface device 20).According to one or more embodiments of the invention, the controlparameters 32 can include input from a portable electronic device and/ora gaming system. For example, the control parameters 32 can includeinput from a gaming system, a portable gaming device, a cellulartelephone, or the like. According to one or more embodiments of theinvention, the controller 30 receives control parameters 32 (e.g.,gaming device input, cellular telephone input, etc.), and does notinclude a sensor 26. According to such embodiments, user input 28 canoptionally be received directly by the controller 30, or can be omittedentirely, depending upon the desired function of the system in which thecontroller 30 is used.

According to one or more embodiments of the invention, the system shownin FIG. 2A can be used in a stand-alone device, such as a cellulartelephone, portable electronic device (e.g., a PDA, etc.), or otherdevice. In a cellular telephone embodiment, for example, feedback can beprovided in the form of haptic sensations via the haptic device 24 inresponse to status events (e.g., a message received signal, a networkindicator signal, etc.), user input (e.g., mode changes, keypad dialing,option selections, etc.), incoming calls, or other events.Alternatively, the system shown in FIG. 2A can be used in aconfiguration, such as the configuration shown in FIG. 1, where aninterface device 20 can be connected to a processor system 10.

FIG. 2B is a block diagram of a haptic device 24 shown in FIGS. 1 and2A. As shown in FIG. 2B, the haptic device 24 includes an actuator 51,an elastic member 52 and a mass 53. The haptic device 24 is configuredto provide haptic feedback. The actuator 51 is operably connected to theelastic member 52, and the elastic member 52 is operably connected tothe mass 53. In operation, the actuator provides force to the elasticmember 52. Some of the force applied to the elastic member 52 istranslated to the mass 53, and causes the mass 53 to move. By causingthe mass 53 to move, haptic forces are provided to a user. Note that theconfiguration shown in FIG. 2B is only one example of a configuration ofa haptic device 24. Other configurations that vary from theconfiguration shown in FIG. 2B can be used as the haptic device 24. Forexample, the elastic member 52 can be coupled to the mass 53 by aflexible coupling; the elastic member 52 can be coupled to the actuator51 by a flexible coupling. In alternative embodiment, the elastic membercan be coupled between actuator and a mechanical ground, and theactuator can be directed coupled to the actuator.

FIG. 3A is a perspective view of a haptic device, according to anembodiment of the invention, and FIG. 3B is a cross-sectional view ofthe haptic device shown in FIG. 3A. As shown in FIGS. 3A and 3B, thehaptic device 100 includes an actuator 110, an elastic member 120 and amass 130. The haptic device 100 is configured to provide hapticfeedback. As with the haptic devices described below, the haptic device100 shown in FIGS. 3A and 3B can be used as the haptic device 24 shownin FIGS. 1 and 2 within an interface device 20.

The actuator 110 of the haptic device 100 is a rotary actuator andincludes a shaft 115. The elastic member 120 includes a proximateportion 121, a compliant portion 122 and a distal portion 125. Theproximate portion 121 of the elastic member 120 is coupled to the shaft115 of the actuator 110. The distal portion 125, which has a widthgreater than the compliant portion 122, is coupled to the mass 130.

The actuator 110 can be any type of rotary actuator such as, forexample, a direct current (DC) motor, voice coil actuator or a movingmagnet actuator. In addition, actuator 110 can be disposed in andmechanically grounded to a device housing (not shown), such as theinterface device 20 described above (e.g., a game controller housing,etc.). Examples of haptic devices disposed in and mechanically groundedto game controller housings are disclosed in U.S. application Ser. No.09/967,494, filed on Sep. 27, 2001, entitled, “Actuator for ProvidingTactile Sensations and Device for Directional Tactile Sensations,” andSer. No. 09/968,725, filed on Sep. 28, 2001, entitled, “DirectionalInertial Tactile Feedback Using Rotating Masses,” the disclosures ofwhich are incorporated herein by reference.

Although the elastic member 120 is shown as being integrally formed in aunitary construction among the proximate portion 121, compliant portion122 and distal portion 125, other configurations are possible. Where thecompliant portion 122 is made of a flexible material, the proximateportion and the distal portion 125 need not be made of flexiblematerials and need not be integrally formed with the compliant portion122. For example, the compliant portion 122 of an elastic member can becoupled to the mass 130 and/or the shaft 115 of the actuator 110 byseparate couplings or fasteners. Similarly, the elastic member 120 canbe of various types including, for example, leaf springs, helicalsprings, and so forth.

The actuator 110, the elastic member 120 and the mass 130 of the hapticdevice 100 collectively have a first operational mode associated with arange of frequencies and a second operational mode associated with arange of frequencies different from the range of frequencies associatedwith the first operational mode. For example, the first operational modecan be based on a unidirectional rotation of the mass 130 about theshaft 115 of the actuator 110 (also referred to herein as the“unidirectional mode”); the second mode can be based on a harmonicmotion of the mass 130 (also referred to herein as the “harmonic mode”).The range of frequencies associated with the first operational mode can,optionally, overlap with the range of frequencies associated with thesecond operational mode.

More specifically, the elastic member 120 coupled between the shaft 115of the actuator 110 and the mass 130 results in a harmonic system. Sucha harmonic system exhibits second order behavior with the magnificationof vibrations at certain frequencies (e.g., at a resonance frequency ofthe mechanical system). Here, the haptic device 100 is configured as aharmonic system where the elastic member 120 stores energy and releasesit while in the harmonic mode. For example, the compliant portion 122 ofthe elastic member 120 can store energy during the movement of the mass130 in response to one polarity of an alternating current (AC) drivesignal and can release the energy during the movement of the mass 130 inresponse to the other polarity of the AC drive signal. This results inharmonic motion and corresponding amplification through broad resonance,which results in high magnitude vibrations and other effects in apower-efficient manner. In addition, complex AC drive signals havingmany different frequency components can be combined (e.g., superimposed,combined by a vectored or non-vectored operation, etc.) on each otherwhile the haptic device 100 operates in the harmonic mode. Thecontroller 30 described above in connection with FIG. 2A provides thesecomplex AC drive signals.

The inventors have recognized that it is advantageous for the dampingfactor of the mechanical system to be low. This may result in a moreefficient harmonic vibration. Consequently, the compliant portion 122 ofthe elastic member 120 can be made of polypropylene, which exhibits alow damping. Alternatively, the elastic member can be made of steel,wire, plastic or other similar types of materials that can connect themass 130 in series with the shaft 115 of the actuator 110.

When operating in the unidirectional mode, the actuator 110 can bedriven, for example, with a DC current, thereby causing the mass 130 torotate about the shaft 115 of the actuator 110 with centripetalacceleration. This centripetal acceleration provides strong inertialforces against the device housing. Firmware or software techniques canbe used to control the magnitude of the vibrations while operating inthe unidirectional mode. For example, a certain pulse-repetition ratehaving a 50% duty cycle results in mass 130 rotating unidirectionally ata certain rate with approximately half of the vibration magnitude thatwould otherwise result from applying a constant voltage (i.e., 100% dutycycle). Although the relationship between the duty cycle and thevibration magnitude may not be linear, it can be approximated as linearover certain operational ranges for the sake of convenience. Furtherexamples of such firmware are disclosed in U.S. application Ser. No.09/669,029, filed on Sep. 27, 2000, entitled, “Controlling HapticSensations for Vibrotactile Feedback,” the disclosure of which isincorporated herein by reference.

When the actuator 110 is operated in the harmonic mode, the mass 130oscillates at or approximately at the frequency of the drive signal(e.g., an AC signal driving the actuator 110). Such a drive signal canbe produced, for example, by an H-bridge circuit or other amplifier. Anexample of an H-bridge amplifier that can be used to produce such adrive signal is disclosed in U.S. application Ser. No. 10/000,662, filedon Oct. 31, 2001, now U.S. Pat. No. 6,683,437, entitled, “CurrentControlled Motor Amplifier System,” the disclosure of which isincorporated herein. Using such a signal advantageously involves smallertime delays in starting and stopping movement of the mass 130 and inachieving peak or maximum acceleration than is the case with motion ofthe mass in the unidirectional mode. Additionally, other techniques maybe employed to reduce time delays associated with starting and stoppingmovement of the mass 130, as will be described below in greater detail,such as providing a lead-in or ending current pulse as part of a controlsignal, for example.

FIG. 4A is a perspective view of a haptic device, according to anotherembodiment of the invention, and FIG. 4B is a cross-sectional view ofthe haptic device shown in FIG. 4A. Unlike FIGS. 3A and 3B, which showan elastic member having a single compliant portion, alternativeembodiments having an elastic member with multiple compliant portionsare possible, such as the haptic device 200 shown in FIGS. 4A and 4B,which has two compliant portions. This haptic device 200 can be used asthe haptic device 24 of the interface device 20 shown in FIG. 1. Thehaptic device 200 includes an actuator 210, an elastic member 220, and amass 230. The actuator 210, which is a rotary actuator, includes a shaft215. The elastic member 220 includes a proximate portion 221, multiplecompliant portions 222, 223, and multiple corresponding distal portions225, 226. The proximate portion 221 of the elastic member 220 is coupledto the shaft 215 of the actuator 210. The distal portions 225, 226 eachhave a width greater than their respective compliant portions 222, 223and are coupled to the mass 230. Although the elastic member 220 shownin FIGS. 4A and 4B has two compliant portions 222, 223, otherembodiments are possible where the elastic member has more than twocompliant portions.

Note that the compliant portion(s) of a rotating mass can be compliantin one degree of freedom or axis of travel of the mass, but need not becompliant in the remaining degrees of freedom. For example, thecompliant portion 122 shown in FIGS. 3A and 3B can be inflexible in thedirection parallel to the axis of rotation along the shaft 115 of theactuator 110. Similarly, the compliant portions 222, 223 shown in FIGS.4A and 4B can each be inflexible in the direction parallel to the axisof rotation along the shaft 215 of the actuator 210. As best shown in4A, the compliant portions 222, 223 can be relatively thick along thedirection parallel to the shaft 215 of the actuator 210. Additionally,the elasticity of the various compliant portions can be varied accordingto torsional or other characteristics.

FIGS. 5-7 each show a top view of a portion of a haptic device inaccordance with other embodiments of the invention. When in operation,the mass(es) for each haptic device rotate(s) about the shaft of theactuator. Each of the portions of haptic devices shown in these figurescan be used either in a unidirectional mode, a harmonic mode, or asuperposition mode that combines the unidirectional mode and theharmonic mode. Thus, each portion of a haptic device shown in FIGS. 5-7has multiple operational modes that can be controlled by way of one ormore embodiments of the invention. Each portion of a haptic device shownin FIGS. 5-7 can also be used as part of the haptic device 24 of FIG. 1.

FIG. 5 shows top view of a portion of a haptic device, according to anembodiment of the invention. The portion 301 of a haptic device in FIG.5 includes an elastic member 320, which is similar to the elasticmembers 120, 220, described above. The elastic member 320 includes aproximate portion 321, a compliant portion 322, and a distal portion325. The proximate portion 321 is coupled to the shaft 315 of anactuator (not shown). The distal portion 325 is coupled to a mass 330.It will be appreciated that the mass 330, although shown as beingintegrally encapsulated within the distal portion 325, can also beexternal to the distal portion 325, according to one or more embodimentsof the invention.

The elastic member 320 shown in FIG. 5 can be used in a unidirectionaloperational mode (e.g., by applying a DC or other low-frequency drivesignal), or in a harmonic operational mode (e.g., by applying an ACdrive signal). Additionally, because the elastic member 320 isasymmetric, it exhibits different characteristics depending on whichdirection it is rotated. Thus, in addition to potentially exhibiting oneof multiple operational modes depending upon the drive signal, differentoperational modes can be achieved by rotating the elastic member 320 ina different direction. Moreover, portion 301 of the haptic device shownin FIG. 5 can provide advantageously a variable moment, whichsubstantially decouples the amplitude and the frequency of hapticsensations produced thereby. More specifically, as the velocity withwhich the portion 301 is rotated increases, the compliant portion 322flexes, and the radial distance between the mass 330 and the center ofrotation (e.g., the shaft 315) varies. For example, according to anembodiment, the mass 330 moves closer to the shaft 315 as the rotationvelocity of the portion 301 increases, thereby changing the moment ofthe portion 301.

FIG. 6 shows a top view of a portion of a haptic device, according toanother embodiment of the invention. The portion 401 of the hapticdevice in FIG. 6 includes an elastic member 420, which is similar to theelastic members 120, 220, 320, described above. The elastic member 420includes a proximate portion 421, a compliant portion 422, and a distalportion 425. The proximate portion 421 is coupled to the shaft 415 of anactuator (not shown). The distal portion 425 is coupled to a mass 430.It will be appreciated that the mass 430, although shown as beingintegrally encapsulated within the distal portion 425, can also beexternal to the distal portion 425, according to one or more embodimentsof the invention.

The elastic member 420 shown in FIG. 6 can be used in a unidirectionaloperational mode (e.g., by applying a DC or other low-frequency drivesignal), or in a harmonic operational mode (e.g., by applying an ACdrive signal). Additionally, as with the elastic member 320 shown inFIG. 5, the elastic member 420 of FIG. 6 is asymmetric, and therefore,exhibits different characteristics depending on which direction it isrotated. Thus, in addition to potentially exhibiting one of multipleoperational modes depending upon the drive signal, different operationalmodes can be achieved by rotating the elastic member 420 in a differentdirection.

FIG. 7 shows a top view of a portion of a haptic device, according to anembodiment of the invention. The portion 501 of a haptic device in FIG.7 includes an elastic member 520, which is similar to the elasticmembers 120, 220, 320, 420, described above. The elastic member 520includes a proximate portion 521, two compliant portions 522, 523, andtwo distal portions 525, 526. The proximate portion 521 is coupled tothe shaft 515 of an actuator (not shown). The distal portions 525, 526are coupled to two masses 530, 532, respectively. It will be appreciatedthat the masses 530, 531, although shown as being integrally containedwithin the distal portions 525, 526, can also be external to the distalportions 525, 526, according to one or more embodiments of theinvention.

The elastic member 520 shown in FIG. 7 can be used in a unidirectionaloperational mode (e.g., by applying a DC or other low-frequency drivesignal), in a harmonic operational mode (e.g., by applying an AC drivesignal) or an operation mode being the superposition of theunidirectional mode and the harmonic mode. Additionally, because theelastic member 520 is asymmetric, it exhibits different characteristicsdepending on which direction it is rotated. This asymmetry of theelastic member 520 can be further accentuated by using differentlyweighted masses 530, 531. Thus, in addition to potentially exhibitingone of multiple operational modes depending upon the drive signal,different operational modes can be achieved by rotating the elasticmember 520 in a different direction.

The portion 501 of the haptic device can also provide a variable moment,which decouples the magnitude and frequency of haptic sensationsprovided thereby. More specifically, the compliant portions 522, 523 canbe formed in such a way to allow the distance between the masses 530,531 to vary as the rotational velocity and/or the direction of rotationof the portion 501 is varied. For example, according to one embodimentof the invention, a compliant member 524 (e.g., a spring) can optionallybe connected between the two distal portions 525, 526. This additionalcompliant member 524 (shown in FIG. 7 by a dashed line) can cause thedistal portions 525, 526 (and the corresponding masses 530, 531) to movecloser together when the portion 501 is rotated in one direction,causing the portion 501 to exhibit a low-frequency eccentric-massresponse. When the portion 501 is rotated in the opposite direction,however, the distal portions 525, 526 (and the corresponding masses 530,531) move farther apart, causing the portion 501 to exhibit ahigher-frequency eccentric-mass response. These two eccentric-massresponses can be used in addition to the unidirectional or harmonicmodes described above to control haptic sensations provided by way of ahaptic device. Thus, for example, the portion 501 can produce amulti-modal response as well as a variable-moment response.

According to one or more embodiments of the invention, the compliantportions 522, 523 of the elastic member 520 are different lengths and/ormade from different materials. For example, materials having differentflexibilities or spring constants can be used to form each of thecompliant portions 522, 523. Additionally, each of the compliantportions 522, 523 can be formed to have different harmonic responses.For example, each of the compliant portions 522, 523 can exhibitharmonic responses to different resonant frequencies or frequencyranges. Additionally, each of the compliant portions 522, 523 canexhibit different responses in each direction or angle of rotation.Thus, depending upon the specific construction of the elastic member520, several harmonic responses and/or several operational modes of theelastic member 520 can be obtained.

According to an embodiment of the invention, a haptic device, such asthe haptic device 24 shown in FIG. 1, for example, includes avariable-stiffness compliant portion of a compliant member. If thespring constant (K) value of a compliant portion of an elastic membercan be varied as a function of drive frequency, then the haptic devicecan operate near a peak magnitude and efficiency across a relativelywide range of frequencies. A mechanical actuator can be, for example, apiezoelectric structure (e.g., a piezoelectric buzzer). Such apiezoelectric structure can include, for example, a ceramic on a masswhere an applied voltage causes movement of the ceramic. Through properselection of the applied voltage, the ceramic can behave in a mannersimilar to a spring. The piezoelectric structure can change its springconstant as a function of bias voltage. Consequently, afrequency-to-voltage converter driving the piezoelectric structure canmaintain a resonance frequency of haptic device by adjusting the springconstant.

The behavior of an embodiment of the haptic device having aunidirectional mode and a harmonic mode (e.g., the haptic device 100shown in FIGS. 3A and 3B, the haptic device 200 shown in FIGS. 4A and4B, and haptic devices using the rotating masses shown in FIGS. 5-7) canbe modeled. Such a model can be based on various factors such as, forexample, the mass shape and weight distribution, and the stiffness ofthe compliant portion of the elastic member. The following provides adynamics model of an embodiment of the haptic device having aunidirectional mode and a harmonic mode.

Equation 1 below is based on a second order Laplace transform function,and can be used to model the harmonic mode of a haptic device, such asthe haptic devices discussed above, for example, which are capable ofusing a rotating mass.

$\begin{matrix}{\frac{X}{T_{m}} = \frac{1}{r\left( {{ms}^{2} + {bs} + k} \right)}} & (1)\end{matrix}$In Equation 1 above, X is displacement of the mass of a haptic device,T_(m) is the torque of an actuator driving the haptic device (e.g., amotor), m is the weight of the mass, r is the eccentricity radius, k isthe spring constant, b is the damping constant, and s is the Laplacevariable. The eccentricity radius r is the distance from center of anactuator shaft to “center of mass” of the mass being driven by theactuator of the haptic device.

Equation 2, shown below, can be used to model the unidirectional mode ofa haptic device, such as the haptic devices discussed above, forexample, which are capable of using a rotating mass.F=rω^(2 m)  (2)In Equation 2 above, F is the force, ω is the angular velocity of themass of the haptic device (e.g., 2πf, where f is the frequency of themass of the haptic device).

Equation 3 below shows a damping ratio d that can be used to modeldamping of a haptic device, such as the haptic devices discussed above,for example, which are capable of using a rotating mass.

$\begin{matrix}{d = \frac{b}{2\sqrt{k}}} & (3)\end{matrix}$In Equation 3 above, d is the damping ratio that relates the dampingconstant b to the spring constant k.

The dynamics model defined above in connection with Equations 1-3 can beused to design a haptic device having a harmonic mode. For example, thespecific values of the damping ratio d, the spring constant k, theweight of the mass m, and the eccentricity radius r can be selected toachieve a particular behavior of a haptic device. Ways in which thedynamics model, defined above using Equations 1-3 can be used to achievea particular behavior of a haptic device is described in greater detailin U.S. application Ser. No. 10/301,809, filed on Nov. 22, 2002,entitled, “Haptic Feedback Using Rotary Harmonic Moving Mass,”incorporated by reference above.

As described above, a multi-mode haptic device is capable of providingeffects using both a unidirectional operational mode and a harmonicoperational mode. According to one or more embodiments of the invention,the unidirectional operational mode provides strong, attention-gettingsignals y, and the harmonic operational mode, on the other hand, is usedto convey subtler sensations than those generally associated with theunidirectional operational mode. In addition to a DC signal, one or moreembodiments of the invention can use a low frequency AC signal can drivea haptic device in the unidirectional operational mode because it hasnon-zero values for sufficiently long periods of time.

FIG. 8 is a plot showing an acceleration-versus-time response of ahaptic device, according to an embodiment of the invention. The responseshown in FIG. 8 is a low-frequency rumble response obtained by applyinga DC drive signal to the haptic device. Or, in other words, the responseshown in FIG. 8 is the response of a haptic device being driven in aunidirectional operational mode.

FIG. 9 is a plot showing an acceleration-versus-time response of ahaptic device, according to an embodiment of the invention. The responseshown in FIG. 9 is obtained by applying an AC drive signal in the formof a periodic square wave having a frequency of approximately 30 Hz. Themagnitude and frequency of the response can be decoupled and can beindependently varied as will be described in greater detail below. Theresponse shown in FIG. 9 can, for example, result from directionreversals caused by the applied periodic square-wave or rectangular-wavesignal. According to one or more embodiments of the invention, anyphysical compliance of the haptic device can cause a recoil, which cancontribute to the response shown in FIG. 9, increasing the size of theacceleration peaks. As discussed above, for rotating masses in anasymmetric device, the compliance may change the moment of the devicedepending upon the direction the device is rotated.

FIG. 10 is a plot showing an example of drive-signal frequency ranges ofa multi-mode haptic device, according to an embodiment of the invention.More specifically, the frequency ranges shown in FIG. 10 are ranges ofdrive-signal frequencies used to drive a bi-modal haptic device having afirst mode that corresponds to the low-frequency range and a second modethat corresponds to a high-frequency range. The principles shown in theplot of FIG. 10 can be generalized, however, to multi-modal hapticdevices having more that two modes, which would have similar, multiplefrequency ranges corresponding to each of the device's multiple modes,and a transitional frequency range between each of those multiplefrequency ranges.

In the example shown in FIG. 10, a low-frequency response is caused bydrive signals within the low-frequency range, which can extend, forexample, from approximately DC (i.e., 0 Hz) to a low-frequency limitf_(low) of approximately 5 Hz. A transitional frequency response iscaused by drive signals within the transitional-frequency range, whichcan extend, for example, from the low-frequency limit f_(low) to ahigh-frequency limit f_(high) of approximately 25 Hz. A high-frequencyresponse is caused by drive signals within the high-frequency range,which can extend, for example, from the high-frequency limit f_(high) toall higher frequencies (e.g., all frequencies capable of being output bythe device). A resonant-frequency f_(res) response, which depends uponthe physical characteristics of the haptic device, is achieved by adrive signal having a frequency located in this example within thehigh-frequency range. For example, the resonant-frequency f_(res)response can be achieved by using drive signals having frequenciesbetween about 60 Hz-200 Hz. The drive signals used to achieve thisresonant-frequency f_(res) response can vary according to designconstraints and desired performance of the haptic device.

The high end of the unidirectional operational mode of the device isdependent upon characteristics of the actuator used. Thus, the exactfrequency where the haptic device ceases to operate in theunidirectional operational mode and begins to operate in the harmonicoperational mode can vary from device to device. Accordingly, thetransitional frequency range is designed to include frequencies of drivesignals at which most actuators transition from operating in aunidirectional operational mode, to operating in a harmonic mode. Thus,the low-frequency range shown in FIG. 10 includes frequencies of drivesignals that can cause some haptic devices to operate in theunidirectional operational mode, and the high-frequency range includesfrequencies of drive signals that can cause these haptic devices tooperate in the harmonic operational mode. Drive signals with frequencieslocated within the transitional frequency range can be used to providesmooth transitions from a low-frequency, unidirectional operational modeto a high-frequency, harmonic operational mode.

FIGS. 11A-11G are plots showing examples of signals used to drive ahaptic device, according to an embodiment of the invention. The signalsshown in FIGS. 11A-11G are low-frequency signals used to drive a hapticdevice within the low-frequency range shown in FIG. 10. These signalsare used to convey a strong sensation and a clear beat pattern of theoutput feedback (i.e., the periodicity of the output feedback) to a userof an interface device, such as the interface device 20 shown in FIG. 1.The signals shown in FIGS. 11A-11G have a period T defined by therelation shown in Equation 4 below.

$\begin{matrix}{T = \frac{1}{f_{desired}}} & (4)\end{matrix}$In Equation 4 above, the desired frequency f_(desired) can be selectedbased upon the desired performance of the haptic device to which thedrive signal is being applied.

According to one or more embodiments of the invention, the desiredfrequency f_(desired) of the drive signal is equal to the resonantfrequency f_(res) of the haptic device to which the signal is beingapplied. When the resonant frequency f_(res) is used to drive anactuator (e.g., by applying the resonant frequency f_(res) directly, orby applying bursts of the resonant frequency f_(res)), acceleration ofthe mass is maximized, and a low frequency response is emulated. Thefrequency of a signal, such as a square wave, can be varied to change auser's perception of a frequency of a haptic effect. The duty cycle canbe varied to change a user's perception of a magnitude of a hapticeffect.

FIGS. 11A-11D are forms of rectangular waves. FIG. 11A is a positivepulse; FIG. 11B is a bipolar pulse; FIG. 11C is a bipolar pulse withinverting polarity; and FIG. 11D is a positive and negative pulse. FIG.11E is a resonant sine pulse and FIG. 11F is a sine pulse train. FIG.11G is a square pulse train.

In accordance with one or more embodiments of the invention, variousduty-cycle-driven control methods for controlling a multi-mode hapticdevice can be used to determine drive frequencies appropriate foremulating low-frequency haptic feedback responses. Such aduty-cycle-driven control method that can be used in accordance with oneor more embodiments of the invention is described in U.S. applicationSer. No. 09/669,029, filed on Sep. 27, 2000, entitled, “ControllingHaptic Sensations for Vibrotactile Feedback,” and Ser. No. 09/675,995,filed on September 29, now U.S. Pat. No. 6,680,729, entitled,“Increasing Force Transmissiblity for Tactile Feedback InterfaceDevices,” the disclosures of which are incorporated by reference.

According to an embodiment of the invention, a duty-cycle-driven controlmethod can be used to divide a frequency range of a haptic device intotwo portions: a low-frequency range and a high-frequency range. Theactuator of the haptic device can be driven using, for example, themaximum available current and/or voltage. According to one or moreembodiments of the invention, a duty-cycle-driven control methodoperates in the unidirectional operational mode. The magnitude of theperiodic haptic feedback is determined by varying the “on-time” of thedriving signal's duty cycle.

According to another embodiment of the invention, using aduty-cycle-driven control method, low-frequency haptic feedback, whichis the rumble response shown in FIG. 8, can be achieved using a drivesignal that has a frequency outside the low-frequency range shown inFIG. 10. The “on-time” t_(on) of the driving signal, according to thisembodiment, is long enough such that the desired haptic feedback isproduced. The maximum magnitude M of the haptic feedback is accomplishedby a drive signal with the maximum on-time t_(onmax). Other magnitudes mof the haptic feedback, which are less than the maximum magnitude M, canbe achieved by using an on-time t_(on) that is less than the maximumon-time t_(onmax), and which is defined in the manner shown below inEquation 5.

$\begin{matrix}{t_{on} = {\frac{m}{M}t_{{on}\mspace{11mu}\max}}} & (5)\end{matrix}$

According to another embodiment of the invention using aduty-cycle-driven control method, high-frequency haptic feedback can beachieved using an on-time t_(on), which is a percentage P of the desiredperiod T. Thus, according to this embodiment, the maximum magnitude Mfor the high-frequency haptic feedback is achieved for an on-time t_(on)that is 100-percent of a specific or desired period T. Other magnitudesm of the haptic feedback, which are less than the maximum magnitude Mcan be calculated in the manner shown below in Equation 6.

$\begin{matrix}{t_{on} = {\frac{mP}{100M}T}} & (6)\end{matrix}$

FIGS. 12A-12C are plots showing examples of signals used to drive ahaptic device, according to an embodiment of the invention. The drivesignals shown in FIGS. 12A-12C have frequencies of approximately 20 Hzto 30 Hz. The signal shown in FIG. 12A, for example, is an example of aunipolar pulse appropriate for operation in the unidirectionaloperational mode. The signal of FIG. 12B is an example of a bipolarpulse with a 50-percent duty cycle appropriate for high-frequencyoperation, or operation in the harmonic operational mode. The signal ofFIG. 12C is an example of a bipolar pulse with a non-fifty-percent dutycycle appropriate for operation in the high-low transition area shown inFIG. 10. The small negative pulse of the signal shown in FIG. 12 C canbe used to stop the motion of the previous period.

According to one or more embodiments of the invention, the drive signalsshown in FIGS. 12A-12C can be used to provide a substantially smoothtransitional frequency range from the low-frequency range to thehigh-frequency range (see, e.g., the transitional frequency range from 5Hz to 25 Hz shown in FIG. 10). As a drive signal transitions from alow-frequency signal to a high-frequency signal, the positive pulse of abipolar signal (e.g., the non-zero-mean bipolar-pulse signal shown inFIG. 12C) is reduced gradually until it becomes a zero-meanbipolar-pulse signal (e.g., as shown in FIG. 12B) causing a hapticdevice to operate in the high-frequency range.

Because the magnitude of the step size from the negative part of thesignal to the positive part of the signal in FIGS. 12B and 12C is largerthan change from zero to the positive part of the signal, it creates alarger perceived haptic effect magnitude. Power is better conserved,however, by not having a negative on-time, as in FIG. 12A. Thus, wherepower conservation is more important, the drive signal using a unipolarpulse (e.g., the drive signal shown in FIG. 12A) can be used, and wherea larger haptic magnitude is required, a bipolar pulse (e.g., the drivesignals shown in FIGS. 12B and 12C) can be used.

FIGS. 13A-13E are plots showing examples of signals used to drive ahaptic device, according to another embodiment of the invention.Generally speaking, the signals shown in FIGS. 13B, 13C, and 13E createa beat pattern easily identifiable by a user because the transients ofthe signal are perceived as a single pulse (e.g., a burst pulse). Thesignals shown in FIGS. 13A and 13D produce a larger perceived magnitudethan the signals of FIGS. 13B, 13C, and 13E, but do not produce a beatpattern as clear as the signals of those Figures in part because oftransients associated with those signals. Thus, as demonstrated by theperceived haptic feedback caused by the drive signals of FIGS. 13A-13E,there is a trade-off between perceived strength and perceived beatpattern.

Drive signals providing haptic feedback within the transitionalfrequency range (see, e.g., FIG. 10) are dependent on the profileschosen in both the low-frequency and high-frequency ranges of a hapticdevice. Specifically, to provide a substantially smooth transitionbetween frequency ranges and consistency of magnitudes over an extendedfrequency spectrum, the proper drive signals within the low-hightransition range can be selected, such that the perceived haptic effectin this area appears to be “blended.”

One technique of combining, or “blending,” drive signals for a smoothresponse transition within the transitional frequency range, accordingto an embodiment of the invention, is to use a resonant pulse, whilevarying the desired frequency. The signal shown in FIG. 14 is a seriesof resonant pulses that can be used to generate drive signals havingfrequencies over the entire functioning frequency range of a hapticdevice, according to an embodiment of the invention. Drive signals inthe low-frequency range can use pulses at a resonant frequency f_(res)spaced at periods T determined by substituting the resonant frequencyf_(res) for the desired frequency f_(desired) in Equation 4. Thisprovides a consistent perceived magnitude and frequency pattern over thewhole functioning frequency range.

Another technique of blending drive signals for a smooth responsetransition within the transitional frequency range, according to aembodiment of the invention, is to use a resonant pulse converted to azero-mean bipolar-pulse periodic signal. Such a signal can be used toprovide haptic feedback within the transitional frequency range. Thetransition drive signal having a zero-mean bipolar-pulse can be derivedusing a magnitude conversion, a frequency conversion, orduty-cycle-driven control method, among other techniques.

FIG. 15 shows a system 600 for performing magnitude conversion of drivesignals according to an embodiment of the invention. A resonant pulsedrive signal generator 602 and a bipolar-pulse drive signal generator604 (e.g., a fifty-percent duty-cycle drive signal generator) producerespective signals computed for the period T in the manner shown inEquation 4. The drive signal produced by each drive signal generator602, 604 is with a corresponding pre-determined weighting filter 606,608, by a corresponding multiplier 610 a, 610 b in the frequency domain.The resulting products are summed by a summer 612 to produce a desiredperiodic profile 614 for the desired frequency f_(desired).

In other words, the resonant pulse generated by the resonant pulsegenerator 602 is multiplied in the frequency domain by a first weightingfilter 606, which is essentially a low-pass filter. The bipolar-pulsedrive signal generated by the bipolar-pulse drive signal generator 604is multiplied in the frequency domain by a second weighting filter,which is essentially a high-pass filter. Hence, in the resulting signalhaving the desired periodic profile 614, as can be seen in the frequencyprofiles of the first weighting filter 606 and the second weightingfilter 608, for frequencies from zero to the low-frequency limit f_(low)shown in FIG. 10, the weight of the resonant pulse is one, and theweight of the bipolar-pulse periodic drive signal is zero, respectively.Conversely, at frequencies from the high-frequency limit f_(high) andabove, the weight of the resonant pulse is zero and the weight of thebipolar-pulse periodic drive signal is one. In the transitionalfrequency range shown in FIG. 10, the resonant pulse signal and thebipolar-pulse drive signal are combined in such a manner that the weightof the resonant pulse signal decreases and the weight of thebipolar-pulse drive signal increases, with increased frequency withinthe transitional frequency range. The resulting desired periodic profile614 provides a haptic feedback having a well-defined pattern that is“blended” across an extended frequency range.

Another technique for blending haptic feedback responses from thevarious frequency ranges shown in FIG. 10, according to anotherembodiment of the invention, is to perform a frequency conversion. Afrequency conversion can be used to smoothly convert a low-frequencyperiodic drive signal that uses a resonant pulse drive signal into ahigh-frequency periodic signal. This technique modifies the frequency ofthe pulse drive signal used in the low-frequency range until the drivesignal is converted to a zero-mean bipolar-pulse (e.g., a fifty-percentduty-cycle periodic signal) at the high-frequency range, similar to themanner discussed above in connection with thetransitional-frequency-range drive signal shown in FIG. 12C.

Equations 7, 8, and 9 refer to an embodiment where the frequency of thepulse f_(pulse) generates haptic feedback that provides a user with aperception of a periodic signal at a desired frequency f_(desired) witha particular magnitude m within the frequencies of the transitionalfrequency range shown in FIG. 10.

$\begin{matrix}{m = \frac{f_{res} - f_{high}}{f_{low} - f_{high}}} & (7) \\{b = {f_{res} - {m \cdot f_{low}}}} & (8) \\{f_{pulse} = {{m \cdot f_{desired}} + b}} & (9)\end{matrix}$In Equations 7, 8, and 9 above, m is the perceived magnitude of thehaptic feedback, f_(low) is the low-frequency limit, f_(high) is thehigh-frequency limit, f_(res) is the resonant frequency of the hapticdevice, and b is the damping constant.

Using Equations 7, 8, and 9 above, the pulse frequency f_(pulse)required to provide a desired frequency f_(desired) haptic output to auser can be readily determined. For example, if a haptic device has aresonant frequency f_(res) of 200 Hz, and the low-frequency limitf_(low) is 5 Hz and the high-frequency limit f_(high) is 25 Hz, thepulse frequencies f_(pulse) required to achieve the perception of thecorresponding desired frequencies f_(desired) are shown in Table 1below.

TABLE 1 Desired frequency Pulse frequency f_(desired) f_(pulse) 5 200 7182.5 10 156.25 12 138.75 15 112.5 17 95 20 68.75 22 51.25 25 25

Using a frequency conversion technique, such as the technique describedabove, the perceived periodicity of haptic feedback experienced by auser is constant over all frequencies, including those within thetransitional frequency range. More specifically, such a frequencyconversion technique provides smooth “blending” of or transitioningbetween effects in the unidirectional operational mode associated withthe low-frequency range and the harmonic operational mode associatedwith the high-frequency range. Additionally, using this frequencyconversion technique, the magnitude of the pulse, which can bedetermined according to Equation 7, is preserved throughout thetransition area, thereby providing haptic feedback having a consistentperceived magnitude to a user.

A duty-cycle-driven control method can also be used to convertlow-frequency signals to a zero-mean bipolar-pulse (e.g., afifty-percent duty-cycle periodic signal) at the high-frequency range,according to another embodiment of the invention. Such duty-cycle-drivencontrol method can be used, for example, with drive signals, such as thedrive signal shown in FIG. 12C. The duty-cycle-driven control method canbe used to determine on-time t_(on) in the same manner determined inboth the low-frequency range and the high-frequency range, as explainedabove in connection with Equations 5 and 6, for example. As describedabove, the negative signal values serve as a brake pulse, or in otherwords, stops the motion associated with the previous pulse.Additionally, as described above, the negative on-time creates a largetransition between positive and negative acceleration (i.e., between thepositive portion of the signal and the negative portion of the signal),which results in a higher acceleration profile and a higher perceivedforce magnitude. The duty-cycle-driven control method achievesrelatively effective periodicity, and increases the strength of theperceived haptic feedback. The duty-cycle-driven control method alsoprovides a smooth perceived transition between all three frequencyranges shown in FIG. 10.

According to one or more embodiments of the invention, periodic hapticresponses in the high-frequency range can be created using one of twotechniques. For example, according to an embodiment of the invention, ahigh-frequency periodic response can be created using a zero-meanbipolar-pulse drive signal, as shown in FIG. 12B. According to anotherembodiment of the invention, a high-frequency periodic response can becreated using a single resonant pulse every period, as shown in FIGS.11A and 11B, for example. Around the resonant frequency f_(res), the twotechniques produce similar periods and magnitudes. Below the resonantfrequency f_(res), however, the zero-mean bipolar-pulse drive signaltechnique generally produces a perceived higher haptic feedbackmagnitude.

According to one or more embodiments of the invention, three distinctdrive signals can be provided for haptic responses within each of thethree frequency ranges shown in FIG. 10. For haptic feedback within thelow-frequency range, a rectangular-wave signal can be provided. Forhaptic feedback within the transitional frequency range, anduty-cycle-driven control method can be used to determine theappropriate drive signal to be applied. For haptic feedback within thehigh-frequency range, a zero-mean bipolar-pulse drive signal can beused.

FIG. 16 is a plot showing an example of a signal used to drive a hapticdevice, according to an embodiment of the invention. Therectangular-wave signal shown in FIG. 16 is used to provide hapticresponses within the low-frequency range shown in FIG. 10. The period Tof the signal is determined by using the desired output frequencyf_(desired), as shown in Equation 4 above. The on-time t_(on) can becalculated using Equations 5 and 6 above. As explained above inconnection with those equations, the maximum on-time t_(onmax)corresponds to the maximum magnitude M of the haptic feedback perceivedby the user. For such an embodiment, for example, the maximum on-timet_(onmax) is about two or three periods of the drive signal (e.g., twoor three rotations of a rotating mass of a haptic device). According toan embodiment of the invention, the maximum on-time t_(onmax) isapproximately 80 milliseconds. This time can vary greatly, however, asit is dependent of the devices used, such as the actuator, mass, andother parameters. The maximum on-time t_(onmax) can be a parameterstored in memory (e.g., in firmware or software, etc.) such that aninterface device 20 can make use of a variety of haptic devices 24, eachof which can have a different set of parameters including a maximumon-time t_(onmax).

According to another embodiment of the invention, a drive signalsupplied within the low-frequency range makes use of only unipolarpulses (i.e., positive-only or negative-only pulses), such as theunipolar pulse signal shown in FIG. 16, for example, to conserve energy,making the haptic device more power efficient. According to yet anotherembodiment of the invention, however, bipolar pulses (i.e., pulseshaving both negative and positive components) can be used to provide aresponse having a better defined periodicity because a negative pulsehas the effect of stopping an effect from a previous positive pulse andvice versa.

FIG. 17 is a plot showing an example of a signal used to drive a hapticdevice, according to an embodiment of the invention. The drive signalshown in FIG. 17 is used to provide haptic sensations within thetransitional frequency range, and is calculated using aduty-cycle-driven control method, such as the ones described above inconnection with Equations 5 and 6. The drive signal in FIG. 17 isbi-directional, which provides a large transition from the negativeportions of the signal to the positive portions of the signal. Thisbi-directional nature of the drive signal produces a larger perceivedmagnitude of the haptic effect generated. The bi-directional nature ofthe drive signal shown in FIG. 17 also stops motion generated from aprevious pulse (i.e., it has a “braking” effect).

The period T of the drive signal shown in FIG. 17 is calculated asdescribed above in connection with Equation 4, using the desiredfrequency f_(desired). As explained above in connection with Equations4, 5, and 6, the maximum on-time t_(onmax) corresponds to the maximummagnitude M of the haptic feedback generated. In one embodiment, theshort negative pulse preceding each positive on-time t_(on) isrelatively short compared to the positive on-time t_(on) and has theeffect of stopping the motion associated with the previous on-timet_(on), but is not perceived by a user (except as a transient artifactof the feedback). For example, the duration of the negative pulse can beapproximately 10 ms.

The duty cycle of the drive signal can steadily increase as the hapticfeedback transitions from the transitional frequency range to thehigh-frequency range shown in FIG. 10. A drive signal having a dutycycle of fifty percent can used in the high-frequency range shown inFIG. 10, such as the drive signal shown in FIG. 12B, for example.

Rectangular-wave drive signals (including, e.g., square-wave drivesignals), such as those described above, are frequently used to convey astrong periodic haptic sensation to a user. These types of sensationsconveyed by the rectangular-wave drive signals are sometimes referred toas “square-like” sensations. These square-like sensations, however, arenot the only type of sensations desired for haptic feedback. Forexample, when a haptic device is being driven in the harmonicoperational mode, or within the high-frequency range, it may beadvantageous to use other drive signal forms because the high-frequencycomponents of such drive signals can be felt and distinguished by usersof a haptic device. Some examples of drive signal shapes that can beused to drive a haptic device in harmonic operational mode to producedifferent haptic sensations than those experienced with a square-wavedrive signal including, for example, a saw-like wave, a sinusoid, or thelike.

FIGS. 18A-18C are plots showing examples of signals used to drive ahaptic device, according to one or more embodiments of the invention.The drive signal shown in FIG. 18A is a square wave similar to thetransitional frequency range drive signal shown in FIGS. 17 and 12C. Thedrive signals shown in FIGS. 18B and 18C are saw-like and sinusoidalwaves, respectively. All of the drive signals shown in FIGS. 18A-18C areconfigured with varying duty cycles using similar techniques to thosedescribed above in connection with FIGS. 17 and 12C with similareffects. Specifically, the drive signals shown in FIGS. 18A-18C have ashort negative pulse prior to the on-time of each drive signal. Thisshort pulse accomplishes a large initial transition, perceived by a useras a larger magnitude of the haptic feedback, and helps stop or slowdown motion of a haptic device from the prior on-time signal (i.e.,performs a “braking” function).

In addition to shaping drive signals used to drive haptic devicescapable of providing multiple operational modes (e.g., unidirectional,harmonic, etc.), other techniques of controlling haptic devices arepossible. For example, whether a haptic device is acting in aunidirectional or harmonic operational mode, a fast response time thatexhibits no perceived lag to a user may be desired. Force applied to ahaptic device (e.g., by way of an applied voltage signal), however,sometimes results in a start-up lag that may be detectable by a user.Such start-up lags can detract from the user's haptic experience forsome applications.

The force F applied to a haptic device, such as the haptic device 24shown in FIG. 1, by a haptic device having rotating mass (e.g., a hapticdevice having an eccentric rotating mass operating in a unidirectionaloperational mode or a haptic device having a harmonic eccentric rotatingmass operating in a unidirectional operational mode) is directlyproportional to the square of the angular velocity ω. This force F canbe calculated as shown below in Equation 10.F=ε _(r)·ω²  (10)

In Equation 10 above, ε_(r) is dependent on the size and shape of therotating mass (i.e., it is dependent on the moment of inertia of themass). This force F can only be detected by a user above a certainthreshold of angular velocity ω. Thus, delays in ramping up the angularvelocity ω of the rotating mass result in a delay of the haptic feedbackfelt by the user. For example, in gaming applications, where the hapticdevice 24 of the user device 20 uses a large rotating mass, this delaycan be as long as approximately 60 ms. Such a significant delay can befelt by a user, and detracts from the haptic sensation experienced bythe user. Thus, in some embodiments, decreasing the delay to synchronizethe visual display of a haptic feedback triggering event with thecorresponding haptic feedback is highly desirable in all operationalmodes, including, for example, the operational modes corresponding tothe three frequency ranges shown in FIG. 10.

FIG. 19A is a plot showing an example of a regular-step drive signal 702a used to drive a haptic device. According to one or more embodiments ofthe invention, this regular-step drive signal 702 a can be referred toas a steady-state signal, or a signal configured to provide steady-statepower to a haptic device. Time is shown in milliseconds on thehorizontal axis, and relative velocity (of the haptic device) is shownon the vertical axis (which is similarly the case for the remainingfigures). The velocity 704 a of the haptic device that results from theregular-step drive signal 702 a is also shown on the same plot as acurve. As can be seen in FIG. 19A, a delay occurs between the initiationof the regular-step drive signal 702 a and the achievement of fullvelocity 704 a (i.e., the steady-state velocity) of the haptic device.In some circumstances, this delay can be perceived by a user, which maybe undesirable in certain applications.

FIG. 19B is a plot showing an example of a signal 702 b used to drive ahaptic device, according to an embodiment of the invention. Thelead-in-pulse drive signal 702 b shown in FIG. 19B incorporates alead-in pulse, and can be used to provide a haptic sensation without alag time associated with a regular-step drive signal (e.g., theregular-step drive signal 702 a shown in FIG. 19A). In other words, thelead-in-pulse drive signal causes an improved velocity 704 b, or reducedresponse time, of the haptic device as shown in FIG. 19B. Thelead-in-pulse drive signal 702 b begins with a pulse configured toaccelerate the haptic device to full velocity quicker than theregular-step drive signal 702 a shown in FIG. 19A. According to anembodiment of the invention, the lead-in pulse of the lead-in-pulsedrive signal 702 b can be provided by quickly discharging a capacitorwhen required. Such a capacitor can be trickle charged, for example, sothat it is capable of providing the lead-in pulse when it is required.

In addition to delays associated with initiating tactile forces (e.g.,haptic feedback), delays also sometimes exist during termination of suchtactile forces (e.g., haptic feedback). For example, because of momentumgained by a rotating mass or other haptic device, termination of a drivesignal does not immediately terminate the motion of the device. Thisresponse-time lag can be detected by users, which may be undesirable incertain applications. The response-time lag is more pronounced in someapplications, such as some video gaming applications that use heavierrotating masses, or other haptic devices having large moments ofinertia.

FIG. 20A is a plot showing an example of a regular-step drive signal 802a used to drive a haptic device. The plot in FIG. 20A shows theregular-step drive signal 802 a, ends as a step function, therebyterminating steady-state power to the haptic device. As can be seen bythe resultant stopping velocity 804 a shown in FIG. 20A, a delay occursin stopping the haptic device, which can be perceived, in somecircumstances, by a user. Such a delay may be undesirable in certainapplications.

FIG. 20B is a plot showing an example of a signal 802 b used to drive ahaptic device, according to an embodiment of the invention. Thebrake-pulse drive signal 802 b used in FIG. 20B includes a portionhaving a negative pulse prior to a potion of the drive signal 802 bhaving zero power. This negative pulse (also referred to as a brake orbraking pulse) results in the improved velocity 804 b shown in FIG. 20B,which has improved stopping characteristics compared to devices using aregular-step drive signal 802 a (shown in FIG. 20A). Specifically, thebrake-pulse drive signal 802 b stops a rotating mass or other hapticdevice more quickly than with a regular step drive signal 802 a. As withthe lead-in-step drive signal 702 b (shown in FIG. 19B), the brake-pulsedrive signal 802 b can be produced, for example, by discharging apreviously charged capacitor.

Drive signals implementing the lead-in pulse and of the lead-in-pulsedrive signal 702 b, and the negative pulse of the brake-pulse drivesignal 802 b can be combined to provide haptic feedback having a reducedlag time (i.e., a reduced response time) at both the beginning and endof the feedback. The drive signals described above in connection withFIGS. 19B and 20B can be created via computer programming code that canbe programmed in software, firmware, or hardware, according to thedesired performance and/or design constraints of the system.

The effects described above in connection with FIGS. 19B and 20B can beimplemented in any of the operational modes (e.g., unidirectional,harmonic, transitional, etc.) associated with the invention.Additionally, these effects can be implemented within all of thefrequency ranges shown in FIG. 10 to provide quicker response withineach of these ranges.

From the foregoing, it can be seen that systems and methods forcontrolling multi-mode haptic devices are discussed. Specificembodiments have been described above in connection with a multi-modehaptic device that has multiple operational modes (e.g., unidirectional,harmonic, etc.), and which operates within multiple frequency rangesincluding: a low-frequency range, a low-high transition range, and ahigh-frequency range. Additionally, specific embodiments have beendescribed in the context of haptic devices using rotating masses toproduce haptic feedback.

It will be appreciated, however, that embodiments of the invention canbe in other specific forms without departing from the spirit oressential characteristics thereof. For example, while some embodimentshave been described in the context of a multi-mode haptic deviceoperating within three frequency ranges, a multi-mode haptic device canhave multiple operational modes that span multiple frequency ranges inexcess of the three discussed above. For example, such a haptic devicecould operate within multiple frequency ranges corresponding to multipleharmonics of the device. These multiple frequency ranges can havemultiple transition frequency ranges therebetween. Additionally, othertypes of actuators, spring-mass systems, and feedback devices can beused to provide haptic device according to the principles of theinvention disclosed above. The presently disclosed embodiments are,therefore, considered in all respects to be illustrative and notrestrictive.

What is claimed is:
 1. A method of creating haptic effects comprising:receiving a haptic signal to generate a haptic effect using a steadystate velocity of a haptic device; determining a first level of powerthat when applied to the haptic device causes the haptic device to reachthe steady state velocity after a first duration of time; generating adrive signal that comprises a second level of power that is higher thanthe first level of power for an initial duration of time, and thatcomprises the first level power after the initial duration of time,wherein the first duration of time is greater than the initial durationof time; and applying the drive signal to the haptic device.
 2. Themethod of claim 1, wherein the haptic device comprises a rotating mass,and the steady state velocity is an angular velocity.
 3. The method ofclaim 1, wherein the second level of power during the initial durationof time comprises a lead-in pulse drive signal.
 4. The method of claim3, wherein the lead-in pulse drive signal is generated by discharging acapacitor.
 5. The method of claim 1, wherein the initial duration oftime is approximately 50 ms, and the first duration of time isapproximately 500 ms.
 6. A method of creating haptic effects comprising:receiving a haptic signal to brake a haptic effect that is generated byapplying a first level of power to a haptic device; generating a drivesignal that comprises a negative pulse for an initial duration of time,and that comprises approximately zero power after the initial durationof time, wherein the negative pulse has an opposite polarity than thefirst level of power; and applying the drive signal to the hapticdevice.
 7. The method of claim 6, wherein the haptic device comprises arotating mass.
 8. The method of claim 6, wherein the negative pulse isgenerated by discharging a capacitor.
 9. The method of claim 6, whereinthe initial duration of time is approximately 50 ms.
 10. The method ofclaim 6, wherein the negative pulse has an approximate opposite level ofpower as the first level of power.
 11. A computer readable medium havinginstructions stored thereon that, when executed by a processor, causethe processor to generate haptic effects, the generating comprising:receiving a haptic signal to generate a haptic effect using a steadystate velocity of a haptic device; determining a first level of powerthat when applied to the haptic device causes the haptic device to reachthe steady state velocity after a first duration of time; generating adrive signal that comprises a second level of power that is higher thanthe first level of power for an initial duration of time, and thatcomprises the first level power after the initial duration of time,wherein the first duration of time is greater than the initial durationof time; and applying the drive signal to the haptic device.
 12. Thecomputer readable medium of claim 11, wherein the haptic devicecomprises a rotating mass, and the steady state velocity is an angularvelocity.
 13. The computer readable medium of claim 11, wherein thesecond level of power during the initial duration of time comprises alead-in pulse drive signal.
 14. The computer readable medium of claim13, wherein the lead-in pulse drive signal is generated by discharging acapacitor.
 15. The computer readable medium of claim 11, wherein theinitial duration of time is approximately 50 ms, and the first durationof time is approximately 500 ms.
 16. A computer readable medium havinginstructions stored thereon that, when executed by a processor, causethe processor to generate haptic effects, the generating comprising:receiving a haptic signal to brake a haptic effect that is generated byapplying a first level of power to a haptic device; generating a drivesignal that comprises a negative pulse for an initial duration of time,and that comprises approximately zero power after the initial durationof time, wherein the negative pulse has an opposite polarity than thefirst level of power; and applying the drive signal to the hapticdevice.
 17. The computer readable medium of claim 16, wherein the hapticdevice comprises a rotating mass.
 18. The computer readable medium ofclaim 16, wherein the negative pulse is generated by discharging acapacitor.
 19. The computer readable medium of claim 16, wherein theinitial duration of time is approximately 50 ms.
 20. The computerreadable medium of claim 16, wherein the negative pulse has anapproximate opposite level of power as the first level of power.